Tire for two-wheel vehicle

Abstract

A tire for two-wheel vehicle includes a tread portion having a designated rotation direction and being provided with a plurality of blocks and grooves. The plurality of blocks includes at least one V-shaped block having an axial center portion located rearwardly in the rotation direction with respect to its axial both end portions and a first sidewall located rearwardly in the rotation direction. The grooves include a groove bottom surface connected to the first sidewall, wherein the groove bottom surface is provided with ribs extending in a tire circumferential direction.

What is claimed is: 
     
       1. A tire for two-wheel vehicle, the tire comprising:
 a tread portion having a designated rotation direction and being provided with a plurality of blocks and grooves; 
 the plurality of blocks comprising at least one V-shaped block having an axial center portion located rearwardly in the rotation direction with respect to both its axial end portions and a first sidewall located rearwardly in the rotation direction; and 
 the plurality of grooves comprising at least one groove having a groove bottom surface connected to the first sidewall, 
 
       wherein
 the groove bottom surface is provided with ribs extending in a tire circumferential direction, 
 the ribs each comprise a rib top surface in a tire radial direction, 
 the rib top surface extends from a rib front end to a rib rear end in the rotation direction, 
 the rib front end is at a position that is connected to the first sidewall, 
 the rib rear end is at a position that is connected to the groove bottom surface, 
 in a tire side view, the rib top surface extends in a straight manner from the rib front end to the rib rear end, and 
 each rib has a groove-bottom connected portion with a length L 2  in the tire circumferential direction that is in a range of 40% to 100% of a length L 3  of the groove bottom surface in the tire circumferential direction. 
 
     
     
       2. The tire according to  claim 1 ,
 the at least one V-shaped block further comprising a keel portion projecting rearwardly in the rotation direction from the axial center portion, and 
 the ribs arranged such that one or some of the ribs exist on each side of the keel portion in a tire axial direction. 
 
     
     
       3. The tire according to  claim 1 , wherein the ribs comprise at least six ribs on the groove bottom surface. 
     
     
       4. The tire according to  claim 3 , wherein the rib front ends of two adjacent ribs of the ribs in a tire axial direction are arranged in different locations from one another in the tire circumferential direction. 
     
     
       5. The tire according to  claim 4 , wherein the rib of the two adjacent ribs that is nearer to a tire equator has the rib front end located rearward in the rotation direction with respect to other ribs of the ribs. 
     
     
       6. The tire according to  claim 1 , wherein the ribs each have a maximum height from the groove bottom surface in a range of from 5% to 30% of a height of the at least one V-shaped block from the groove bottom surface. 
     
     
       7. The tire according to  claim 1 , wherein the at least one V-shaped block comprises a plurality of V-shaped blocks located on a crown region of the tread portion, and constitute a crown block row of crown blocks. 
     
     
       8. The tire according to  claim 7 , wherein the plurality of blocks comprises
 a pair of middle block rows each comprising middle blocks and arranged outwardly in a tire axial direction of a respective side of the crown block row, 
 a pair of shoulder block rows each comprising shoulder blocks arranged outwardly in the tire axial direction of a respective middle block row, 
 with respect to each of the crown blocks, each of the middle blocks which is arranged nearest to the concerned crown block is located forwardly in the rotation direction relative to the concerned crown block, and 
 with respect to each of the middle blocks, one of the shoulder blocks arranged nearest to the concerned middle block is located forwardly in the rotation direction relative to the concerned middle block. 
 
     
     
       9. The tire according to  claim 1 , wherein a distance W 2  in a tire axial direction between a tire equator and an axially innermost arranged rib of the ribs is equal to or more than 15% of a width W 1  in the tire axial direction of the at least one V-shaped block. 
     
     
       10. The tire according to  claim 9 , wherein a width W 3  in the tire axial direction of each rib is in a range from 2% to 10% of the width W 1  of the at least one V-shaped block. 
     
     
       11. The tire according to  claim 1 , wherein the rib front ends of two adjacent ribs of the ribs in a tire axial direction are arranged in different locations from one another in the tire circumferential direction. 
     
     
       12. The tire according to  claim 1 , wherein a height H 1  in the tire radial direction from the groove bottom surface to the rib front end is smaller than a length of the rib top surface. 
     
     
       13. The tire according to  claim 1 , wherein a height H 1  in the tire radial direction from the groove bottom surface to the rib front end is smaller than the length L 2 . 
     
     
       14. The tire according to  claim 1 , wherein the length L 2  is in a range of 50% to 100% of the length L 3 . 
     
     
       15. The tire according to  claim 1 , wherein the length L 2  is in a range of 60% to 100% of the length L 3 . 
     
     
       16. The tire according to  claim 1 , wherein the length L 2  is equal to the length L 3 .